XXX.—Thermal and Electric Conductivity

1878 ◽  
Vol 28 (3) ◽  
pp. 717-740 ◽  
Author(s):  
Tait
Keyword(s):  
Thermal Conductivity ◽  
Electric Conductivity ◽  
Marked Effect ◽  
Original Method ◽  
The State ◽  
British Association ◽  
Pure Metals ◽  
The Absolute

The following paper contains the results of an inquiry which has occupied me at intervals for somewhere about ten years. It was carried out in part at the expense of the British Association, and I have already reported results to that body in 1869 and 1871. But these provisional reports referred to very short ranges of temperature only, and the experiments were made with faulty thermometers, for which I had not the corrections which had been carefully determined by Welsh at Kew.The inquiry arose from my desire to extend to other metals the very beautiful and original method which Principal Forbes devised, and which the state of his health prevented him from applying to any substance but iron. Forbes' experiments gave a result so very remarkable, and (as it seemed to me) so theoretically suggestive, that I wished to extend them to other pure metals, and also, in one or two cases at least, to alloys.I believe that Principal Forbes had at least two reasons for undertaking his investigations:—(1.) When he commenced his inquiry, there was no really accurate or trustworthy determination of the absolute conductivity of any body whatever for heat. (2.) FORBES had himself, in 1833 and subsequent years, pointed out a very remarkable analogy between the conducting powers of metals for electricity and for heat, and had shown that these were almost precisely proportional to one another—that is to say, that the list of the average relative conductivities of different metals for electricity differed, from that of their relative conductivities with regard to heat, certainly not more than did the several electric lists furnished by different experimenters, and certainly less than the corresponding thermal lists. Hence it was natural to suppose that temperature might have a marked effect on thermal conductivity, as it was known to have such an effect on electric conductivity.

scholarly journals I. Experiments, by the method of Lorentz, for the further determination of the absolute value of the British association unit of resistance, with an appendix on the determination of the pitch of a standard tuning-fork

1883 ◽  
Vol 34 (220-223) ◽  
pp. 438-439
Keyword(s):  
Tuning Fork ◽  
British Association ◽  
Cavendish Laboratory ◽  
Absolute Value ◽  
The Absolute ◽  
The Difference

The experiments described in the present paper were carried out during the spring and summer months of the present year, at the Cavendish Laboratory, and are divided into three distinct series. In the first and second series, the induction coils were situated nearly in the plane of the revolving disk, as in Lorentz’s original use of the method; the difference between the two series relating only to the speed of rotation, which was varied in the proportion of 10:16.

scholarly journals The thermal conductivity of carbon dioxide

1927 ◽  
Vol 114 (767) ◽  
pp. 354-366 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Free Path ◽  
Critical Pressure ◽  
Mean Free Path ◽  
Double System ◽  
Wire Method ◽  
The Mean ◽  
The Absolute ◽  
The Many

Of the many experimental determinations of the thermal conductivity of Co 2 which have been made, the absolute values given by the various observers vary from 3·07 × 10 -5 cal. sec. -1 cm. -1 deg. -1 (Winkelman, 1), to 3·39 × 10 -5 cal. sec. -1 cm. -1 deg. -1 (Weber, 2), and generally speaking the experiments were modifications of two principal methods, namely, the electrically heated wire of Schleimacher (3) and the cooling thermometer method. In both of these methods convection losses were present to a degree depending on the dimensions and disposition of the apparatus, and on the pressure of the gas; therefore, in the author’s opinion, the discrepancies amongst various observers are due to the practice of attempting to eliminate these convective losses by diminishing the pressure. Such a procedure is justifiable only if the reduction of pressure is not carried beyond the point at which the mean free path of the molecules becomes comparable with the dimensions of the containing vessel. This is a critical point in the determination of the conductivity of a gas, as the authors’ experiments on Co 2 indicate that the convection becomes negligible only at pressures for which the mean Free Path Effect is such that the significance imposed on the conductivity by Fourier’s law loses its meaning, and below this critical pressure the conductivity varies with the pressure in a manner depending on the dimensions of the vessel containing the gas. In the experiments of Gregory and Archer (4), on the thermal conductivities of air and hydrogen, the use of a double system of electrically-heated wires enabled the authors accurately to identify the critical pressure at which convective losses became negligible. This is an extremely important point in all applications of the hot-wire method to the absolute determination of the conductivities of gases, and alone justifies the procedure of lowering the pressure to eliminate convective losses. Above this critical pressure it is necessary to disentangle the conduction and convection losses, and below, the meaning of conduction loses its ordinary significance.

scholarly journals The thermal conductivities of oxygen and nitrogen

1928 ◽  
Vol 118 (780) ◽  
pp. 594-607 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Temperature Coefficient ◽  
Thermal Conduction ◽  
Standard Substance ◽  
The Absolute ◽  
Thermal Conductivities

The interest in the determination of the thermal conductivities of oxygen and nitrogen lies partly in their relation to the thermal conductivity of air. The latter is the medium which practically every experimenter on gaseous thermal conduction has investigated, and has therefore become the standard substance in this field of research. Being a mixture chiefly of the gases oxygen and nitrogen, with the latter in the greater proportion, the value of its conductivity should lie between those of oxygen and nitrogen and should be nearer that of nitrogen than that of oxygen. The authors, in common with Weber and Todd, have verified this experimentally, the only observer finding these con­ductivities in a contrary order being Winkelman, who used a cooling thermometer method. The following is a table of the results hitherto obtained for the absolute thermal conductivities at 0° C. of oxygen and nitrogen, together with their authors’ results for air. The values marked with an asterisk have been deduced by applying the temperature coefficient, 0.0029 per 0° C., to results which were obtained at temperatures above 0° C. Weber has recently published a new result for the thermal conductivity of air, 0.0000574, which is about 1 per cent. higher than his old value. Assuming that, if his results for oxygen and nitrogen were revised, they would be increased in the same proportion, his new values for these gases would be—oxygen 0.0000583, and nitrogen 0.0000572.

scholarly journals X. The absolute thermal conductivities of iron and copper

1893 ◽  
Vol 184 ◽  
pp. 569-590 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Experimental Work ◽  
University College ◽  
Different Temperatures ◽  
The Absolute ◽  
Thermal Conductivities

The experiments described in this paper were undertaken at the suggestion of Pro­fessor A. Gray, M. A., University College, Bangor, with the object of contributing something to the results still necessary to establish the experimental work bearing on the absolute thermal conductivity of metals on a more satisfactory basis. They were also intended to furnish a determination of the absolute conductivity of pure copper at different temperatures. The data already accumulated on the thermal conductivities of iron and copper are due chiefly to Ångström, Forbes, Neumann, Tait and Mitchell, and more recently to Kirchhoff and Hansemann and Lorenz.

scholarly journals X. An experimental determination of the values of the velocities of normal propagation of plane waves in different directions in a biaxal crystal, and a comparison of the results with theory

1879 ◽  
Vol 170 ◽  
pp. 287-377 ◽  
Keyword(s):  
Experimental Determination ◽  
Plane Waves ◽  
British Association ◽  
Method Section ◽  
Wave Surface ◽  
The Absolute ◽  
Comparison Of The Results ◽  
Iceland Spar ◽  
Normal Propagation

Part I. Preliminary.-Professor Stokes's Report to the British Association, 1862, with Outline of the Method. Section I.-Review of Previous Experiments and Criticism of Fresnel's. In his report to the British Association in 1862, Professor Stokes says: "The exactness of the spheroidal form, assigned by Hughens to the sheet of the wave surface within Iceland spar, does not seem to have been tested to the same degree of rigour as the ordinary refraction of the ordinary ray; for the methods applied by Wollaston (Phil. Trans., 1802, p. 381) and Malus (Mem. de l'Institut Sav. Etran., tom. ii., p. 303, 1811) for observing the extraordinary refraction can hardly bear comparison for exactness with the method of prismatic refraction adopted for the ordinary ray; and observations on the absolute velocities of propagation in different directions within biaxal crystals are almost wholly wanting.

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